Chromium (Cr6+) is needed or can be generated in industries such as chromium chemical, passivation of steel-making cold-rolled sheet, chemical plating and tanning, and a great deal of waste water containing chromium (Cr6+) will be produced. Chromium is one of high toxic elements and can cause severe environment pollution when being directly discharged, grievous injury such as skin ulceration, inflammation of respiratory tract, anemia and neuritis can be resulted from human body contact or intake, and it also one of known carcinogen.
At present, harmless treatment of the waste water containing chromium (Cr6+) mainly includes chemical reduction and sealed landfill after precipitation. If waste containing chromium (Cr3+) residues are discharged or buried after being treated, environment pollution can still be caused in the long run. Documents show that the—waste water containing chromium (Cr6+) can also be concentrated, extracted and recycled by using an extraction method. However, since extraction is performed under high acidity (the pH value being about 2) condition, and reverse extraction is performed under strong alkaline (the alkali concentration being greater than 1M) condition, so a great amount of agents will be consumed, and a great deal of high salinity waste water can be generated which is hard to treat. Moreover, the strip liquor is low in concentration, and produce high post-treatment expense in post-treatment.